Hose can best be described as a flexible pipe. Its purpose is to contain and transmit fluid from one location to another safely. Fluids include liquid, gas, solids in a fluidic state and combinations of these categories. Hose has advantages over pipe inasmuch as it is flexible, it absorbs vibration, it may handle corrosive fluids, it comes in a great variety of sizes, it is sound dampening, and is easily stored.
Hose is constructed of three basic elements, (1) the tube or inner liner which is the element which contains, conveys and resists the fluid inside. It transmits the forces created by internal pressure of the fluid to the strength member of the hose; (2) the reinforcement or strength member of the hose, commonly referred to as "hose reinforcement", reacts to and resists the forces of the fluid pressure; and (3) the cover which protects the hose reinforcement from physical damage and resists the external environment.
Materials used to construct the tube or inner liner and the cover consists of, in the most common cases, rubber or plastic, while the hose reinforcement usually comprises yarns, fabrics, and metal in the form of filaments, wires, fabric, braid, spirals, etc. Rubber is used in its broad sense including all elastomeric materials--natural, synthetic, and compounds and structures thereof, while plastics include the wide spectrum of thermoplastic materials. The hose reinforcement includes materials made from cotton, synthetics, or combinations thereof, and metals include steel, copper, aluminum, and platings thereon such as zinc, brass, cadmium, and tin.
Available today are a wide range of basic elastomers to choose from, and many types can be blended together in almost unlimited combinations to obtain different properities. Common rubbers available are neoprene, natural rubber, polyisoprene, butyl, nitrile, SBR, hypalon, ethylene, propylene, chloronated polyethylene (CPE), fluorocarbons, epichlorohydrin, and epichlorohydrin/ethylene oxide. Examples of thermoplastic materials include polyvinyl chloride (PVC), polyethylene (PE), nylon, polyester, polyurethane (TPU), and EVA. In addition, fibers commonly used in hose construction comprise cotton, rayon, glass, nylon, polyester, asbestos, fiber B, and nomex nylon.
The five basic types of hose reinforcements are identified by the method of manufacture or application over the inner tube or liner. These five types are braid, spiral, wrapped ply, loom, and knit. In braiding, a braid is formed by interweaving cords while they are being applied in a helical spiral over the tube. One-half of the cords are spiraled right-hand, and the other left-hand. The most common hose braiding machines weave cords in a two-over, two-under pattern. When multiple plies are braided, it is important to obtain proper adhesion between plies as well as to the tube and cover. Adhesion is usually obtained by the use of a thin layer of tie gum, often called friction, or by a dough or cement application in and around cores of the braid.
Spiral reinforcement is applied in separate plies. The first ply is laid in a left-hand spiral and the second ply is laid in a right-hand spiral. Successive plies are applied in a similar manner, each ply separated by a tie gum layer or dough adhesive. Wrapped ply reinforcement of a woven fabric is often used as hose reinforcement, either as a series of multiple plies, or in conjunction with a spiral wire. The fabric is prepared by calendering or coating the fabric with rubber compound, i.e., tie gum, which enables the fabric to adhere to adjacent plies, to the tube, and to the cover. In addition, the tie gum may first be applied to the tube and then wrapped with the woven fabric. Loom reinforcement of hose is made with cords wound at a closed circular pitch while longitudinal (wrap) yarns are interwoven with the circular wound cords. Knit reinforcement of hose is accomplished by applying reinforcing yarns over the tube in a circular knitting machine. Variations of the knit pattern include a plain knit, lock-stitch, or wrap knit.
For more extensive information, the reader is referred to the publication, HOSE HANDBOOK, Rubber Manufacturers Association, 1901 Pennsylvania Avenue, N.W., Washington, D.C. 20026 (1979).
The inner tube or liner must be firm enough in the unvulcanized state to resist deformation and stretch under normal processing conditions described above. When the tube is too thin or too soft to withstand subsequent processing, or when the internal diameter must be kept within a narrow range, it is supported on a mandrel. The mandrel is at least as long as the hose to be made and has a round or other cross-section as desired.
In many cases, hoses utilized for pressurized liquids are wrapped with hose reinforcement applied under tension and the material chosen for the inner tube is not sufficiently firm to resist deformation and stretch and therefore must be vulcanized prior to application of the tie gum and hose reinforcement. In addition, many times the inner tube must be supported on an internal mandrel during this method of processing. The present state of the art in constructing hose for pressurized liquids is to employ a mandrel at least as long as the hose to be made, the mandrel being removed either before or after vulcanization of the tie gum and hose cover. If the mandrel is removed prior to final vulcanization, the interior of the hose is supported during vulcanization by gas under pressure.
Because of the problems that are inherent in removing the mandrel from a completed hose (before or after final vulcanization), hose length has been limited in construction to lengths which can be physically handled during processing and where the mandrel can be removed without substantial danger of harming the hose.
As a consequence, when long lengths of hose are desired, it is necessary to join pieces of hose to achieve the long lengths. This results in discontinuities of all the members of the hose at the point of joinder. In addition, it is common for hose normally flexible to be more rigid at the points of joinder, whether the joinder be by method of metal coupling, or through build-up of additional material holding both ends of the hose together.
It is to this end that the subject inventive method is directed, i.e., to present a method of fabricating virtually unlimited length hose having no discontinuities therein.